Load distribution and redundancy using tree aggregation

ABSTRACT

A network comprising a plurality of trees each comprising at least one ingress leaf node, at least one interior node, and at least one egress leaf node, wherein at least some of the ingress leaf nodes and the egress leaf nodes are common to the trees, and wherein the ingress leaf node is configured to transport data to the egress leaf node using any of the trees is disclosed. Also disclosed is a network component comprising a processor configured to implement a method comprising selecting one of a plurality of trees associated with information contained within a frame, directing the frame to the selected tree, and maintaining a filtering database (FDB) entry in an interior node in the unselected tree or trees.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 60/968,426, filed Aug. 28, 2007 by Robert Sultan,et al. and entitled “System and Method of Load Distribution andRedundancy Using Tree Aggregation,” which is incorporated herein byreference as if reproduced in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Service providers may offer Ethernet-based connectivity to customersusing the methods specified by Institute of Electrical and ElectronicsEngineers (IEEE) standard 802.1Q Virtual Local Area Network (VLAN)Bridging and its amendments, including IEEE 802.1ad Provider Bridging(PB) and IEEE 802.1ah Provider Backbone Bridging (PBB). IEEE 802.1Qspecifies that the active components of a VLAN Bridged network mustconform to a tree topology in order to avoid looping of frames. Such atree topology may be maintained dynamically by a Spanning Tree Protocol(STP) or statically by provisioning or by the use of a network having aphysical tree topology. A node that has only a single point ofattachment to the tree (i.e., which lies at the edge of the tree) iscalled a leaf node. Any other node is called an interior node.

In the tree topology, data communications can be protected against linkfailures using the IEEE 802.3ad standard, also referred to as LinkAggregation. According to Link Aggregation, the data transported betweentwo nodes is distributed among a plurality of links between those nodes,which are said to belong to a Link Aggregation Group (LAG). When a linkfails, the data load assigned to that link can be reassigned or shiftedto other available links in the LAG. Thus, Link Aggregation providesload distribution and protection against link failures withoutaddressing node failures. Other methods have been proposed to supportload distribution and to provide protection against both link and nodefailures. However, such methods may require establishing a virtualswitch architecture, where the interior nodes are paired andinterconnected via dedicated links or trunks to form a virtual interiornode and hence provide redundancy against node or link failures.Accordingly, the interior node's functionality is modified or upgraded,which may not be desired by a service provider.

SUMMARY

In one embodiment, the disclosure includes a network comprising aplurality of trees each comprising at least one ingress leaf node, atleast one interior node, and at least one egress leaf node, wherein atleast some of the ingress leaf nodes and the egress leaf nodes arecommon to the trees, and wherein the ingress leaf node is configured totransport data to the egress leaf node using any of the trees.

In another embodiment, the disclosure includes a network componentcomprising selecting one of a plurality of trees associated withinformation contained within a frame, directing the frame to theselected tree, and maintaining a filtering database (FDB) entry in aninterior node in the unselected tree or trees.

In a third embodiment, the disclosure includes a method comprisingidentifying a plurality of trees in communication with an egress leafnode, and sending a plurality of frames to the egress leaf node bydistributing the frames among the trees.

These and other features will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a schematic diagram of an embodiment of a tree networkarchitecture.

FIG. 2 is a schematic diagram of an embodiment of a tree aggregationgroup (TRAG) network architecture.

FIG. 3 is a schematic diagram of an embodiment of a TRAG networkarchitecture in which the TRAG does not extend to all bridging deviceswithin the network.

FIG. 4 is a flowchart diagram of an embodiment of a tree aggregationmethod (TRAM).

FIG. 5 is a schematic diagram of an embodiment of a general-purposenetwork component.

DETAILED DESCRIPTION

It should be understood at the outset that although an illustrativeimplementation of one or more embodiments are provided below, thedisclosed systems and/or methods may be implemented using any number oftechniques, whether currently known or in existence. The disclosureshould in no way be limited to the illustrative implementations,drawings, and techniques illustrated below, including the exemplarydesigns and implementations illustrated and described herein, but may bemodified within the scope of the appended claims along with their fullscope of equivalents.

Disclosed herein are a TRAG network architecture and a TRAM forsupporting load distribution across the portion of a network within thescope of the TRAG and providing protection against link and nodefailures within the scope of the TRAG. The TRAG may comprise a pluralityof trees, each comprising a plurality of nodes connected in a treetopology. In an embodiment, the trees of the TRAG are connected tocommon leaf nodes while being disjoint at the interior nodes. Hence, theredundancy of the network may be improved by modifying the leaf nodeswithout modifying the interior nodes. The TRAM may comprise distributingdata loads across the trees in the TRAG by hashing on the source mediaaccess control (MAC) address (SA), destination MAC address (DA),combination of SA and DA, or any other fields in the frame that mayserve to identify a flow at a TRAG ingress leaf node. The data may thenbe transported across the trees in a connectionless manner. If a link ornode failure is detected in one tree, then the load assigned to thattree may be reassigned to at least one other tree. Additionally, aplurality of FDB entries may be refreshed in at least some of theinterior nodes using special control frames to prevent or reduce networkflooding in the case of link or node failures.

FIG. 1 illustrates one embodiment of a tree network architecture 100.The tree network architecture 100 comprises a plurality of interiornodes 120 in communication with a plurality of leaf nodes 130 as shownin FIG. 1. The leaf nodes 130 may in turn be in communication with aplurality of end-stations 140. While the tree network architecture 100in FIG. 1 is symmetrical, the tree network architecture 100 may also beasymmetrical. The network may utilize the IEEE 802.1D Bridging protocol,the IEEE 802.1Q VLAN Bridging protocol, the IEEE 802.1ad ProviderBridging protocol, the IEEE 802.1ah Ethernet Backbone Bridging Protocol,or other suitable protocols.

The tree network architecture 100 may comprise at least one interiornode 120. An interior node 120 may be connected to at least one leaf 130node via point-to-point links and may be connected to one or more otherinterior nodes 120 via point-to-point links. These links may beelectrical, optical, wireless, or other type of communications link.Communications within the network flow from one leaf node 130 to anotherleaf node 130 via some sequence of interior nodes 120. As such, eachleaf node 130 may be coupled to at least one end-station node 140 thatoriginates (sources) or receives (sinks) data frames. Further, the leafnodes 130 may be at the edge of the network or may be part of theinterior of the network.

The interior nodes 120 and leaf nodes 130 may comprise an IEEE 802.1D orIEEE 802.1Q Bridging device or other device or component configured totransport frames between a source end-station node 140 and a destinationend-station node 140. Such devices typically contain a plurality ofingress ports for receiving frames from other nodes, logic circuitry todetermine which port or ports on which the forward frames, and aplurality of egress ports for transmitting frames. In an embodiment, theinterior nodes 120 and leaf nodes 130 make the determinations needed totransport the frames through the network at Open System Interconnection(OSI) layer two.

The load transported between a source end-station node 140 and adestination end-station node 140 may comprise frames, such as Ethernetframes or any similar information structure. In embodiments, theidentifier may include a SA, a DA, or both. Additionally, the identifiermay include a tag protocol identifier (TPID) and a VLAN identifier (VID)as defined by IEEE 802.1Q.

FIG. 2 illustrates an embodiment of a TRAG network architecture 200,which may be established for networks that support a tree networkarchitecture, such as the tree network architecture 100. The TRAGnetwork architecture 200 may comprise a plurality of trees eachconfigured similar to that of the tree network architecture 100. Eachtree may comprise the same number of levels and the same number of nodesat each level as shown in FIG. 2, or they may have different numbers oflevels and nodes. In an embodiment, the trees are disjoint, that is theymay not share any common nodes except at the leaf node level. As such,at least some and preferably all of the leaf nodes are common to the setof trees, while the interior nodes corresponding to the different treesare disjoint.

For instance, the TRAG network architecture 200 may comprise two trees,as shown in FIG. 2. The first tree (represented by the solid lines) maycomprise a first interior node 220 at the top-level connected to aplurality of interior nodes 220 at a second level via point-to-pointlinks. In turn, each first interior node 220 may be connected to aplurality of leaf nodes 230 at a third level via point-to-point links.Similarly, the second tree (represented by the dashed lines) maycomprise a second top-level interior node 212 connected to a pluralityof interior nodes 222 at the second level via point-to-point links. Inturn, each second interior node 222 may be connected to a plurality ofleaf nodes 230 at the third level via point-to-point links. In addition,the leaf nodes 230 are in communication with a plurality of end-stationnodes 240 (represented by the dashed and dotted lines). In anembodiment, each interior node of the first tree 220 is disjoint fromthe corresponding interior node of the second tree 222, and each leafnode 230 of the first tree is common with each leaf node 230 of thesecond tree.

The source and destination end-station nodes 240, identified by SA orDA, are below the leaf nodes 230. Specifically, each leaf node 230 mayhave one or more of end-station nodes 240 associated with it. Each leafnode 230 may perform the functions of an ingress leaf node or an egressleaf node with respect to frames passing through that node. As usedherein, the ingress and egress leaf nodes may be defined as nodes thatare connected to a plurality of trees. A leaf node performs the leafingress function when the leaf node transmits a frame towards or intothe TRAG. A leaf node performs the leaf egress function when the leafnode transmits a frame away from the TRAG.

In an embodiment, the data frames may be transported between the sourceend-station 240 and destination end-station 240 via the nodes associatedwith a single tree, similar to the forwarding scheme of a tree networkarchitecture, such as the tree network architecture 100. For example,the data frames may be forwarded via the first tree along a routeillustrated by the solid lines comprising two leaf nodes 230, twosecond-level interior nodes 220, and one top-level interior node 220.Alternatively, the data frames may be forwarded via the second treealong a route illustrated by the dashed lines comprising the same twoleaf nodes 230, two second-level interior nodes 222, and the top-levelinterior node 222. In another embodiment, the load of one leaf node 230may be distributed or forwarded along more than one tree. For example,some of the frames may be forwarded via the first tree along a routecomprising two leaf nodes 230 and three interior nodes 220, while theremaining frames may be forwarded via the second tree along a routecomprising the same two leaf nodes 230 and three interior nodes 222.Specifically, an ingress leaf node may direct frames associated to oneor another of the trees based on the identity of a flow associated withthe frames. The flow may be identified by performing a hash function onparticular fields associated with the frame including, but not limitedto, the SA and/or DA. For example, an ingress leaf node may receiveframes from four ingress end-stations 240, each identified by an SA. Insuch a case, the leaf node may send the frames from the first twoend-stations 240 to the tree indicated by the solid lines and the framesfrom the last two end-stations 240 to the tree indicated by the dashedlines. As such, the TRAG network architecture 200 may provide loaddistribution to increase the network bandwidth capability, improvenetwork availability or resilience to link or node failures, or both.

When a node or link associated with one tree fails, at least some of thedata frames may be redirected by the ingress leaf node to another tree.For example, when a point-to-point link in the first tree fails, theload assigned to the first tree may be transferred to the second tree.Alternatively, the load for the first tree may be distributed over aplurality of trees when there are at least three trees.

FIG. 3 illustrates another embodiment of a TRAG network architecture300. Similar to the TRAG network architecture 200, the TRAG networkarchitecture 300 may comprise a plurality of trees. However, the TRAG inFIG. 3 does not include all nodes in the physical tree topology. Inparticular, the nodes 350 of the physical topology are not included inthe TRAG. Specifically, the first tree may comprise interior nodes 320and leaf nodes 330. The second tree may comprise interior nodes 322 andleaf nodes 332. Non-TRAG nodes 350 perform frame forwarding and are partof the network, but are not associated with disjoint trees as in thecase of TRAG nodes. In such a case, the eight end-station nodes 350 onthe right side of FIG. 3 forward frames to non-TRAG nodes 350 which, inturn, forward the frames to leaf nodes 330 or 332 and thence to interiornodes 320 or 322 as appropriate.

In an embodiment of the TRAG network architecture, at least some ofnodes may comprise a Filtering Database (FDB). The nodes may use the FDBentries to forward the frames received from the direction of an ingressleaf along one of the trees towards the egress leaf node. For instance,the FDB may comprise a plurality of entries, each consisting of a MACaddress and VID and an associated egress port. In an embodiment, theingress leaf node may match the received frames' DA and VID to one ofthe table entries and forward the frames via the associated port. TheFDB may be populated by analyzing a frame's SA and VID and associatingthat MAC address with the port on which the frame was received. Whenframes associated with a particular source end-station, identified by anSA, are not directed on a given tree, then the FDB of nodes along thatgiven tree will not contain an FDB entry associated with that MACaddress. If a failure occurs in a node or link of some other tree in theTRAG, then traffic will be redirected to the given tree. If theredirected traffic references the unlearned MAC address as a destinationaddress, then frames will be flooded until the MAC address is learned.This is likely to occur for many MAC address values, and excess floodingwill result in network disruption. Specifically, if the ingress leafnode hashes frames based on their SA, then each tree will only receive aportion of the SAs associated with the ingress leaf node and the FDBentries in the other trees will age out. For instance, the node's FDBmay not comprise a particular MAC address if it has not been receivedwithin the previous ten minutes. As such, the node's FDB entries may notcomprise the forwarding information needed to forward the frames to theegress leaf node when the load from the failed tree is redistributed.Hence, the nodes on the reassigned tree may forward the frames to allthe egress ports, i.e., flood the connected nodes with traffic, toguarantee that a copy of the frames is received by the appropriate node.Flooding the nodes with traffic may consume additional bandwidth andresources in the network, which may lead to network traffic congestionor other connectivity problems. As such, the ingress leaf node mayperiodically send a TRAG control frame (TCF) on the various trees tomaintain the FDB entries. The egress leaf node may drop the TCF uponreceipt.

The TCF may comprise the same MAC header as the data frames, e.g. it hasthe same SA and DA, but does not comprise the payload. Each time theingress leaf node transmits a data frame on one of the trees, it mayforward a TCF along the other trees comprising the TRAG, therebyrefreshing the FDB entries in the nodes along the trees on which thedata frame is not being sent. However, this may increase the amount ofcontrol traffic in the network. Alternatively, the ingress leaf node mayforward the TCF with some probability, P. Specifically, the ingress leafnode may use a probability generator to determine whether to send a TCFto the trees (e.g., those trees upon which the frame was not sent) wheneach frame is processed. The value of P may be between zero and one andmay be adjusted to increase or decrease the likelihood and/or frequencywith which TCFs are sent to the various paths. Higher probabilitiesincrease the likelihood that a given FDB entry will be present, andtherefore reduce the likelihood of subsequent flooding, but at theexpense of additional control traffic. Conversely, decreasedprobabilities reduce control traffic, but increase the likelihood offlooding.

Alternatively, the ingress leaf node may forward the TCF at a framefrequency that is preset with respect to the number of forwarded framesalong the assigned tree. For example, the ingress leaf node may forwardone TCF every about 100, about 1,000, or about 10,000 transmitted dataframes. Such rates may be based on the data rates such that the TCFsreach the various nodes' FDBs prior to the FDBs' internal aging orexpiration time. Alternatively, the ingress leaf node may forward theTCF at a time frequency. For example, the ingress leaf node may preset atimer to a predetermined time period, and forward the TCF each time thetimer expires. The predetermined time period may be less than or equalto about the FDBs internal aging or expiration time. The process may berepeated as long as the data frames are being forwarded along theassigned tree.

Frames traversing a VLAN Bridging device are normally forwarded on aport or ports determined by a lookup of DA and VID fields of the frame.The result of the lookup is an outbound port. In the case that the frameis forwarded on a TRAG, the result of the lookup is a ‘TRAG Port’. TheTRAG port is a logical port rather than a distinct physical port.Similarly, when a frame is received, the port on which it arrived isassociated with the DA and VID it contains. When the frame arrives via aphysical port associated with a TRAG, the logical TRAG port that islearned and installed in the FDB. Thus, when a frame is to be forwardedon the TRAG, and a function (e.g., hashing function) is applied tofields in the frame to identify the particular tree on which the frameis to be forwarded, this operation can be viewed alternatively as themapping of a logical TRAG port to a physical Bridge Port.

Where an interior node of a tree represents a VLAN Bridging device, thedevice forwards traffic associated with a particular VLAN only on thoseports associated with the VID carried by a frame. The bridges receiveVLAN membership information via a MAC Address Registration Protocol(MRP) VLAN Registration Protocol (MVRP). When the interior nodes of TRAGmember trees are disjoint from one another, an interior node in one treemaintains the same forwarding associations as the corresponding interiornode in another tree. This may be accomplished by forwarding an MVRPmessage to be transmitted on the TRAG port on the physical portassociated with each of the member trees. In this way, the VLAN portmembership list will be the same for corresponding interior nodes ofdifferent trees of the TRAG.

FIG. 4 illustrates an embodiment of a TRAM 400 for handling reroutingand forwarding of frames in a TRAG. The TRAM 400 may be implemented todistribute the load among a plurality of paths corresponding to aplurality of trees in the TRAG. Additionally, the TRAM 400 may maintainthe FDB entries by sending a TCF from the ingress leaf nodes of thetrees. When a link or node in a tree fails, and the frames are forwardedvia an alternative tree, flooding may be reduced or substantiallyeliminated by using the TCF to maintain FDB entries.

At block 410, the TRAM 400 may determine whether the status of any treehas changed since the last time such a check was made. The status isdetermined based on a connectivity check performed distinctly on eachtree using the methods specified by IEEE 802.1ag Connectivity FaultManagement (CFM). At block 460, a data structure representing each ofthe trees is updated with a marking indicating whether that tree isoperational or failed based on the status change detected at block 410.At block 420, it determined whether a frame is waiting to be sent on thelogical port associated with the TRAG. If not, processing returns toblock 410, otherwise processing proceeds to block 430.

At block 430, the TRAM 400 determines the tree on which the frame shouldbe forwarded. For example, a hash function is applied to specifiedfields of the frame. The result of the hash identifies the tree on whichthe frame is to be forwarded. If the selected tree is not operational,then a second hash function is applied that re-associates the frame withan operation tree. At block 440, the TRAM 400 identifies the physicalport to which the selected tree is mapped. The TRAM 400 then sends theframe on the physical port associated with the selected tree.

At block 450, the TRAM 400 may optionally send at least one TCF alongone or a plurality of backup trees. For example, the TCF may be sentaccording to any of the methods described herein. The TRAM 400 may usethe TCF to update or refresh the forwarding information at the nodes'FDBs along the backup tree or trees. The TCF may be received at thenodes along the trees and may be used to update the FDBs entries.Accordingly, the nodes' FDBs that receive the TCF at a higher rate, forexample at every about 100 forwarded data frames or at a probability of90 percent (P=0.9), may be updated more frequently than the nodes' FDBsthat receive the TCF at a lower rate, for example at every about 1,000forwarded data frames or at a probability of 20 percent (P=0.2). Assuch, the possibility of having the FDBs at the backup path updated atany instance or at the instance of detecting a failed primary assignedtree may increase as the frequency of forwarding the TCF is increased.However, increasing sending the TCFs and updating the nodes° FDBs alongbackup trees more frequently may increase the amount of network controltraffic.

The network components described above may be implemented on anygeneral-purpose network component, such as a computer or networkcomponent with sufficient processing power, memory resources, andnetwork throughput capability to handle the necessary workload placedupon it. FIG. 5 illustrates a typical, general-purpose network component500 suitable for implementing one or more embodiments of the componentsdisclosed herein. The network component 500 includes a processor 502(which may be referred to as a central processor unit or CPU) that is incommunication with memory devices including secondary storage 504, readonly memory (ROM) 506, random access memory (RAM) 508, input/output(I/O) devices 510, and network connectivity devices 512. The processor502 may be implemented as one or more CPU chips, or may be part of oneor more application specific integrated circuits (ASICs).

The secondary storage 504 is typically comprised of one or more diskdrives or tape drives and is used for non-volatile storage of data andas an over-flow data storage device if RAM 508 is not large enough tohold all working data. Secondary storage 504 may be used to storeprograms that are loaded into RAM 508 when such programs are selectedfor execution. The ROM 506 is used to store instructions and perhapsdata that are read during program execution. ROM 506 is a non-volatilememory device that typically has a small memory capacity relative to thelarger memory capacity of secondary storage 504. The RAM 508 is used tostore volatile data and perhaps to store instructions. Access to bothROM 506 and RAM 508 is typically faster than to secondary storage 504.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods might beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

1. A network comprising: a plurality of trees each comprising at leastone ingress leaf node, a plurality of interior nodes, and at least oneegress leaf node, wherein the interior nodes of each tree are completelydisjoint from each other, wherein at least some of the ingress leafnodes and the egress leaf nodes are common to the trees, wherein theingress leaf node is configured to transport data to the egress leafnode using any of the trees, wherein a leaf node sends a plurality ofdata packets associated with a Source Address (SA) on a selected treebut not on an unselected tree, wherein the leaf node periodically sendsan Ethernet packet that lacks a data payload on the unselected tree,thereby causing the unselected tree to maintain a Filtering Database(FDB) entry corresponding to the SA, wherein the unselected tree doesnot receive any data packets associated with the FDB entries beforereceiving the non-data packet, and wherein at least some of the nodesare Ethernet bridges.
 2. The network of claim 1, wherein the ingressleaf nodes are in communication with a plurality of source end-stations,and wherein the egress leaf nodes are in communication with a pluralityof destination end-stations.
 3. The network of claim 1, wherein the dataassociated with one tree is transported from the ingress leaf node tothe egress leaf node via at least one other tree when the one treeexperiences a link or node failure.
 4. The network of claim 1, whereinthe data associated with one tree is transported from the ingress leafnode to the egress leaf node via at least one other tree when the onetree experiences a link or node failure.
 5. The network of claim 1,wherein there is no synchronization between interior nodes.
 6. Thenetwork of claim 1, wherein the network is an IEEE 802.1D BridgedNetwork, an IEEE 802.1Q VLAN Bridged Network, an IEEE 802.1ad ProviderBridged Network, or an IEEE 802.1ab Provider Backbone Bridged Network.7. A network component comprising: a processor configured to: select oneof a plurality of trees associated with a frame; direct the frame to theselected tree; and maintain a Filtering Database (FDB) entry in aninterior node in the one or more unselected trees, wherein maintainingthe FDB entry comprises sending a control frame on the one or moreunselected-trees, and wherein the control frame comprises a Media AccessControl (MAC) header but lacks a data payload.
 8. The network componentof claim 7, wherein the control frame is sent on the one or moreunselected trees periodically, and wherein a frequency with which thecontrol frame is sent is determined using a probability.
 9. The networkcomponent of claim 7, wherein the control frame is sent on the one ormore unselected trees periodically, wherein a frequency with which thecontrol frame is sent is determined using a timer or a counter, andwherein the timer or the counter has an interval that is less then orabout equal to an aging interval of the FDB.
 10. The network componentof claim 7, wherein the frame comprises the MAC header and a payload.11. The network component of claim 7, wherein sending the control frameon the one or more unselected trees comprises sending the control frameon both a first unselected tree and a second unselected tree, whereinthe first unselected tree is associated with a first probability and thesecond unselected tree is associated with a second probability that islower then the first probability and wherein the processor is furtherconfigured to direct a second frame comprising the MAC header andpayload down the selected tree; determine whether to updated a first FDBentry in the first unselected tree and a second FDB entry in the secondunselected tree based on the first probability and the secondprobability, respectively, and responsive to the determination, send thesecond control frame down the first unselected tree without sending thesecond control frame down the second unselected tree, wherein the secondcontrol frame comprises the MAC header but lacks a data payload.
 12. Amethod comprising: identifying, by an Ethernet bridge, a plurality oftrees in communication with an egress leaf node, wherein the treescomprise a plurality of Ethernet nodes; selecting at least one but notall of the trees; sending a plurality of frames associated with a SourceAddress (SA) to the egress leaf node by distributing the frames over theselected trees; and maintaining a Filtering Database (FDB) entrycorresponding to the SA in each unselected tree by sending a controlframe to each unselected tree, wherein the control frames each comprisea Media Access Control (MAC) header but lack a data payload.
 13. Themethod of claim 12, wherein the frames are forwarded by the trees in aconnectionless manner.
 14. The method of claim 12, wherein either thetrees do not extend to all nodes in the network, or at least some of theegress leaf nodes are not adjacent to any end-stations.
 15. The methodof claim 12, wherein a logical tree aggregation group (TRAG) port ismaintained as an outbound port entry in an a-FDB, wherein the logicalTRAG port is later translated to a physical bridge port associated witha specific tree for purposes of frame forwarding, and wherein a logicalTRAG port is learned based on a second frame having been received on aphysical port associated with one of the trees.
 16. The method of claim12, wherein a MAC Address Registration Protocol (MRP) virtual local areanetwork (VLAN) Registration Protocol (MVRP) message to be sent on thelogical tree aggregation group (TRAG) port is forwarded on the physicalport associated with each tree associated with the TRAG.
 17. The methodof claim 12, wherein the frames associated with the SA comprise the MACheader and a data payload.
 18. The method of claim 17, wherein theunselected trees do not receive any frames comprising the MAC headerdata that are associated with the SA within a predetermined time periodbefore receiving the control frame, wherein the predetermined timeperiod is about: equal to a filtering database (FDB) aging interval. 19.The method of claim 12, wherein each of the trees comprise a pluralityof interior nodes, and wherein the interior nodes of at least one of thetrees are disjoint from a plurality of interior nodes in each of theother trees.
 20. The network component of claim 7, wherein the controlframe is an Ethernet frame that lacks an Ethernet payload.
 21. Themethod of claim 12, wherein the control frames are Ethernet frames thatlack an Ethernet payload.